Carbon film, field emission cathode comprising the carbon film, and method of manufacturing the carbon film

Abstract

In a field emission film used for a field emission cathode, a filamentous structure layer is formed in the vicinity of tops of acicular projections to emit electrons. The filamentous structure layer serves to remarkably increase emission points and, as a result, to improve an emission current density. The filamentous structure layer may be composed of a carbon and is obtained by carrying out plasma processing within a hydrogen gas and/or an oxygen gas for a long time.

What is claimed is:  
     
         1 . A carbon film comprising an acicular carbon layer and a filamentous carbon layer which is covered on the acicular carbon layer.  
     
     
         2 . A carbon film as claimed in    claim 1   , wherein the acicular carbon layer comprises a plurality of conical and/or pyramidal shape projections.  
     
     
         3 . A carbon film as claimed in    claim 2   , wherein the projections have bottom widths that are not greater than 200 nm.  
     
     
         4 . A carbon film as claimed in    claim 1   , wherein the filamentous carbon layer is formed by at least one carbon filament that is not greater than 10 nm in filament width.  
     
     
         5 . A film for use in emitting electrons, the film comprising a filamentous layer formed by a plurality of filaments.  
     
     
         6 . A film as claimed in    claim 5   , wherein the filamentous layer is attached to an acicular layer.  
     
     
         7 . A film as claimed in    claim 6   , wherein the acicular carbon layer comprises a plurality of acicular projections.  
     
     
         8 . A film as claimed in    claim 7   , wherein the acicular projections have conical and/or pyramidal shapes.  
     
     
         9 . A film as claimed in    claim 5   , wherein the filamentous layer is composed of carbon.  
     
     
         10 . A film as claimed in    claim 6   , wherein both the filamentous layer and the acicular layer are formed by carbon.  
     
     
         11 . A field emission cathode comprising an emitter for emitting electrons, wherein the emitter comprises a carbon film which has a composite layer structure.  
     
     
         12 . A field emission cathode as claimed in    claim 11   , wherein the composite layer structure has an acicular carbon layer and a filamentous carbon layer which is covered on the acicular carbon layer.  
     
     
         13 . A field emission cathode as claimed in    claim 12   , wherein the acicular carbon layer comprises a plurality of conical and/or pyramidal shape projections.  
     
     
         14 . A field emission cathode as claimed in    claim 13   , wherein the filamentous carbon layer is formed by at least one carbon filament that is not greater than 10 nm in filament width.  
     
     
         15 . A method of manufacturing a composite carbon film, comprising the steps of: 
 depositing a carbon film;    forming an acicular carbon layer composed of acicular projections on a surface of the carbon film; and    changing the acicular carbon layer into a filamentous carbon layer comprising at least one filament to form the composite carbon film.    
     
     
         16 . A method as claimed in    claim 15   , wherein the forming step comprising the step of: 
 carrying out plasma processing of the carbon film within a hydrogen gas to form the acicular carbon layer;    the changing step comprising the step of:    carrying out plasma processing the acicular carbon layer within a hydrogen gas to form the filamentous carbon layer attached to the acicular carbon layer and to thereby form the composite carbon film.    
     
     
         17 . A method as claimed in    claim 15   , wherein the forming step comprising the step of: 
 carrying out plasma processing of the carbon film within a hydrogen gas and an oxygen gas to form the acicular carbon layer;    the changing step comprising the step of:    carrying out plasma processing the acicular carbon layer within a hydrogen gas to form the filamentous carbon layer attached to the acicular carbon layer and to thereby form the composite carbon film.    
     
     
         18 . A method of manufacturing a field emission cathode which has an emitter, comprising the steps of: 
 depositing a carbon film;    forming an acicular carbon layer composed of acicular projections on a surface of the carbon film; and    changing the acicular carbon layer into a filamentous carbon layer comprising at least one filament to form the emitter.    
     
     
         19 . A method as claimed in    claim 18   , wherein the forming step comprising the step of: 
 carrying out plasma processing of the carbon film within a hydrogen gas to form the acicular carbon layer;    the changing step comprising the step of:    carrying out plasma processing the acicular carbon layer within a hydrogen gas to form the filamentous carbon layer attached to the acicular carbon layer and to thereby form the emitter.    
     
     
         20 . A method as claimed in    claim 18   , wherein the forming step comprising the step of: 
 carrying out plasma processing of the carbon film within a hydrogen gas and an oxygen gas to form the acicular carbon layer;    the changing step comprising the step of:    carrying out plasma processing the acicular carbon layer within a hydrogen gas to form the filamentous carbon layer attached to the acicular carbon layer and to thereby form the emitter.